The API token should be available once you log on to https://dtm.adobe.com and visit Account Settings from the Profile icon on top-right. This step is not required from the Asset Insights perspective because the integration of AEM Sites with Asset Insights is still in the works.

The code calls assetAnalytics.dispatcher.init() after making sure that _satellite.getToolsByType('sc')[0].getS() is initialized and assetAnalytics,dispatcher.init is available. This is the reason why you can skip adding it in step 11.

As indicated in comments within the Insights Page Tracker code (Tools > Assets > Insights Page Tracker), when Page Tracker does not create an AppMeasurement object, the first three arguments (RSID, Tracking Server, and Visitor Namespace) are irrelevant. Empty strings are passed instead to highlight this.
The remaining arguments correspond to what is configured in the Insights Configuration page (Tools > Assets > Insights Configuration).

The AppMeasurement object is retrieved by querying satelliteLib for all available SiteCatalyst engines. If multiple tags are configured, change the index of the array selector appropriately. Entries in the array are ordered as per SiteCatalyst tools available in the DTM interface.

Save and close the Code Editor window, and then save the changes in the Tool configuration.

In the Approvals tab, approve both the pending approvals. The DTM tag is ready for insertion in your web page. For details on how to insert DTM tags in web pages, see Integrating DTM in custom page templates.